Todd, I've never been able to calc 800 gpm through 1", but as I believe I have heard Roland say at least once the velocity issue is a self correcting phenom. At a certain point in your system no matter how much pressure you throw at it, the velocity is going to check itself by causing pipe to be upsized. I do not like to see high velocities in my calcs (over 32 fps), but on occasion it does happen. I can't see where lowering velocity, as an example, from 37 fps down to 32 fps is justified by increasing pipe size on a job that has a couple of thousand feet of pipe. The sprinkler system will still function correctly at 37 fps as it would at 32 fps. The only difference I see is that the 32 fps system is now going to cost someone a whole bunch more than the 37 fps system. Back to Pu = $S.
bk -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Todd Williams - FPDC Sent: Monday, June 02, 2008 9:51 AM To: [email protected] Subject: Re: High velocities It sounds like I'm the only one out there not designing systems with Mach 3 velocities. There has to physically be some upper limit to what a pipe can carry. You're not going to get 800 gpm through a piece of 1", even though you can calculate the friction loss with HW. Where is the practical limit? (Joe may be able to shed some insight. hint, hint....) At 11:27 AM 6/2/2008, you wrote: >The formula that I was taught some time back is, Pu = $s (pressure >unused equals dollars spent). > >BK > >-----Original Message----- >From: [EMAIL PROTECTED] >[mailto:[EMAIL PROTECTED] On Behalf Of >Fletcher, Ron >Sent: Monday, June 02, 2008 9:12 AM >To: [email protected] >Subject: RE: High velocities > >Burn it up! > >-----Original Message----- >From: [EMAIL PROTECTED] >[mailto:[EMAIL PROTECTED] On Behalf Of Chris >Cahill >Sent: Monday, June 02, 2008 7:47 AM >To: [email protected] >Subject: High velocities > > > >A question for where there is healthy pressures. Around here 60 is >considered high. I know places with 28 static. > Got a OHII system that needs to be changed to EXII. > That's not negotiable. It's a 40 yo pipe schedule system. That >appears to be in good shape. The BL need to be replaced for 100 sq.ft. >but the main even the last 12' >of 2.5", 25' of 3" and 36' of 3.5" can fly without being replaced. The >openings are where I need them. There is a FP with about 140 psi at >the 900gpm demand. The "problem" >is the velocities in one segment of pipe are just about 40 (last piece >of 3") and about 30 in the 3.5". I quote problem because I know 13 has >no limit, this is not FM. > There is still better than 15 psi safety. > >So the question is where you have pressure do you typically burn it up >with small pipe size at the cost of velocities getting high or do you >leave a lot of safety? > Again not FM and OK per 13. > >Any thoughts on why this is a bad idea? It's easy to say just pull the >offending pipe. In reality though you all know the competitive market >and spending owners money. > > >Chris Cahill, P.E. >Fire Protection Engineer >Sentry Fire Protection, Inc. > >763-658-4483 >763-658-4921 fax > >Email: [EMAIL PROTECTED] > >Mail: P.O. Box 69 > Waverly, MN 55390 > >Location: 4439 Hwy 12 SW > Waverly, MN 55390 _______________________________________________ Sprinklerforum mailing list [email protected] http://lists.firesprinkler.org/mailman/listinfo/sprinklerforum To Unsubscribe, send an email to:[EMAIL PROTECTED] (Put the word unsubscribe in the subject field)
